If you are really worried about the sheeting thickness on your wing centre section, I have three suggestions:

1) 1/16 = 2/32 so you could laminate another 1/32 sheet on top of the existing sheet to get the desired thickness

OR

2) Fibreglass the entire wing centre section with light glass cloth

OR

3) Don't worry about it, 1/16 balsa will give adequate strength along with all the spruce and balsa used for ribs and spars.